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Re: Lighting damage to concrete foundation

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Jim,

I discussed this situation with a colleague who is a retired Ph.D. having spent most of his career in reinforced concrete materials technology. He has never personally experienced lightning striking concrete before. The results of our discussion went something like the following.

We do not think that there is any change in the chemistry or other characteristics of the concrete. We have no scientific knowledge to back this opinion; this is just our personal expectation.

We think that if the electric current traveled through the foundation this current flow would result in very high current flow in the reinforcing steel. We don't believe that this would affect the properties of the steel in any long term way. However, it could conceivably heat the steel to a high level which may change the metallurgy; others on the list will know more about metallurgy than I do. Hot reinforcing will probably expand and could cause cracking and delamination of the concrete in much the same way that corrosion of the steel (such as parking structures, for example) would do.

       I hope these thoughts are useful to you.

This is a very interesting problem. Please post your findings in the list if you can.

Regards,

H. Daryl Richardson


----- Original Message ----- From: "Jim Wilson" <wilsonengineers(--nospam--at)yahoo.com>
To: <seaint(--nospam--at)seaint.org>
Sent: Monday, August 22, 2005 9:30 AM
Subject: Lighting damage to concrete foundation


I had a call from a residential client with a house
struck by lightning.  She claimed that the lightning
entered the house through a septic line and blew the
interior foam insulation off the inside wall of the
poured concrete foundation.  The lightning then
traveled through the foundation and blew the
insulation off of a couple of other areas.

I've never heard of such a thing but it got me
wondering if lightning can damage either the chemical
structure of cured concrete or if it can damage the
reinforcing steel.  Supposedly, there is some cracking
in these areas, but no one's sure if it is new or not.
I couldn't take a stab at that assessment until I had
a look at it.

Any thoughts?  It sounds liks the insurance company is
waiting for a professional opinion of how much
investigation is required to assess the problem.

Jim Wilson, P.E.
Stroudsburg, PA

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